Used in targeted cancer therapy, particularly for non-small cell lung cancer and other solid tumors overexpressing HER3. Binds to the extracellular domain of HER3, inhibiting activation of the PI3K/AKT signaling pathway, which reduces tumor cell proliferation and survival. Investigated in combination with other agents like EGFR inhibitors or chemotherapy to overcome resistance and enhance antitumor efficacy. Also serves as a reference standard in biosimilar development and immunoassay validation.